Radio frequency identification (RFID) technology is currently used for providing wireless automated identification of various devices. An RFID system generally includes a transponder called a “tag,” which is carried by the device to be identified, and an radio frequency (RF) tag reader, which communicates with the transponder. In particular, the RF transponder, in response to a wireless interrogation signal transmitted by the RF tag reader via an antenna, wirelessly transmits an identification code back to the RF tag reader, which decodes the code and sends it onto a host processor or computer for identification of the device. RF transponders may either be passive, semi-passive, or active. Passive transponders parasitically obtain operating power from the wireless signal transmitted by the RF tag reader, whereas semi-active and active transponders obtain their power from on-board batteries.
RFID technology has many applications including: identifying aircraft in order to avoid collisions in the case of commercial aircraft or avoid friendly fire in the case of military aircraft; identifying employees at secured locations by placing a security card in close proximity to a card reader; and identifying optical media, such as compact disks (CDs), CD-ROMs, and digital versatile disks (DVDs). In the latter case, the incorporation of RFID technology into optical disks has been identified to be a solid value proposition opportunity in: i) on-the-disk anti-counterfeiting techniques whereby copy privileges are eliminated or limited when a specific code is read from the RFID transponder (assuming that the target optical drive has an RFID reader); ii) counterfeit detection at the point of entry into the destination country; iii) royalty tracking for content owners; and iv) supply chain track and traceability programs (assuming that the goods owner wants to track at the individual component level).
In the first scenario, the RFID reader need only be a few millimeters (e.g., 5 millimeters) from the RF transponder, which will typically take the form of a small passive integrated circuit (IC) chip mounted on the optical disk. Thus, the use of a low-gain antenna with the RF transponder, often times within the IC itself, which can be conveniently incorporated into the hub of the optical disk, will typically be sufficient to provide robust communication between the RF transponder and reader in this situation. In the last three scenarios, however, the RFID reader must be capable of communicating with the RF transponder from up to a few feet away. This is because the optical disks transported within the supply chain between the manufacturer and the retailer are typically packaged in cartons or “master packs”, which will be further arranged on pallets. Thus, when scanning each pallet of optical disks, an RFID reader typically cannot be placed in close proximity to most, if not all, of the physical media.
Because the passive RF transponder chips currently incorporated into optical disks do not have the range necessary to activate in response to wireless signals received from the RFID reader a few feet away, the range of the RF transponder chip must be increased by either coupling an external portable power source in the form of a battery to the RF transponder chip (basically transforming it into a semi-passive or active transponder), or coupling a high gain antenna to the RF transponder chip.
The use of a battery on an optical disk, however, is not recommended for several reasons. First, the additional weight of the battery will tend to disrupt the delicate dynamic balance needed to rotate optical disks within disk drives at high speeds—typically at thousands of revolutions a minute. Second, batteries tend to leak their contents over time, resulting in damage to the optical disk, specifically the reflective surface. Third, batteries have a limited life, and thus, the efficacy of the RF transponder chip will be lost over time. Although this would not necessarily cause problems for royalty and supply chain tracking, which presumably would be accomplished before the end of battery life, any anti-counterfeiting functionality of the RF transponder chip would be lost once the battery was expired.
The option of coupling a high gain antenna to the RF transponder chip creates additional challenges. Unlike with other applications, such as tracking aircraft, where the space available for incorporating a relative large antenna is virtually unlimited, the space available on an optical disk is severely limited—not only by the limited total area of the optical disk, but also by desire not to adversely affect the data storage region of the optical disk (i.e., the concentric region of the disk from which data is optically read).
Besides enabling RFID transponders to be read from relatively great distances, it is also desirable to incorporate RFID technology into optical disks in a manner that is both tamper-proof and minimizes the risk of damage to optical disk drives. For example, RF transponder chips may be conveniently applied to the surface of already formed optical disks, e.g., using an RFID enabled label that is applied post-disk fabrication, thereby obviating the need to alter the disk fabrication process. However, this solution avails a nefarious person the opportunity of circumventing the anti-counterfeiting features of the RFID technology simply by peeling the label and accompanying RFID transponder off of the optical disk. Further, there is an ever-present risk that that the label substrate adhesive can, in some cases, transfer to the drive clamping mechanism, thereby potentially risking damage to the optical reader.
There thus remains a need to incorporate RFID technology into optical disks that can be activated at relative great distances, is tamper-proof, and minimizes the chance of damage to disk drives.